Evaluation of blood loss and significance of postoperative autotransfusion in knee joint alloplasty.

BACKGROUND: The aim of this paper is to evalute perioperative blood loss associated with total cemented knee joint alloplasty, with special regard to specific factors that may influence this loss. Additionally, the significance of postoperative autotransfusion in these procedures is assessed. MATERIALS AND METHODS: The study group consisted of 85 patients (61 females and 24 males); in 32 cases a postoperative autotransfusion system was used (CBCII ConstaVac, Stryker). Factors analysed comprised pre- and postoperative hemoglobin levels, drain blood loss, heterologous blood transfusion volume and reasons for the transfusion, including co-morbidities. RESULTS: Allogeneic blood transfusion was necessary in 54.72% of the patients who did not have autotransfusion and in 34.38% of the patients who received autotransfusion. The mean volume of blood collected in the drains was 882 ml, while the mean volume of reinfused blood amounted to 524.2 ml. Hypertensive patients experienced greater postoperative blood loss. The average drop in hemoglobin levels was 3.6 g/dl and was smaller by 0.6 g/dl in patients who received autotransfusion. The lowest preoperative hemoglobin values occurred in patients who required heterologous blood transfusion despite autotransfusion. Heterologous blood transfusion was performed at a hemoglobin level of 8.4 g/dl; in patients with a concomitant ischemic heart disease the cut-off value was 9.6 g/dl. CONCLUSIONS: 1. The average drop in hemoglobin levels associated with knee alloplasty was 3.5 g/dl. The volume of recovered blood used for post-operative autotransfusion was approx. 500 ml. 2. A low preoperative hemoglobin level is the most significant risk factor for heterologous blood transfusion. 3. Co-mordibities need to be taken into consideration when determining the amount of blood required.